How self-etch adhesives can help prevent sensitivity

June 15, 2013

As patients’ expectations for both the form and function of their dental restorations increase, clinicians must be prepared to perform high-quality work that meets patients’ high standards and keeps them comfortable.

As patients’ expectations for both the form and function of their dental restorations increase, clinicians must be prepared to perform high-quality work that meets patients’ high standards and keeps them comfortable.

While it is not something patients can generally see or appreciate, the bonding procedure can have a major effect on the long-term comfort and performance of a restoration. Even practitioners who are confident in their technique may face challenges with post-operative sensitivity because of the bonding procedure.

Because of this, it is important for practitioners to understand the strengths and weaknesses of their adhesive systems and to apply them appropriately. In most cases, a self-etch adhesive such as 3M™ ESPE™ Easy Bond Self-Etch Adhesive can give practitioners the most confidence in preventing post-operative sensitivity.

How self-etching systems work 

It is important to understand how self-etching systems avoid the sensitivity associated with total-etch adhesives. With a total-etch system, a phosphoric acid etchant is applied to etch the surfaces of dentin and enamel. This allows the adhesive to form a micromechanical bond with these etched surfaces.

Because untreated enamel has minimal porosity, the phosphoric acid serves to demineralize the enamel, increasing the surface area available for bonding. The adhesive can then penetrate the porosities and form an interlocking bond. On dentin, acid etching removes the smear layer, opens the dentin tubules, and demineralizes the intertubular dentin. The adhesive can then penetrate the open dentin tubules and into the collagen fiber network of the intertubular dentin.

When the collagen layer is hydrated, these fibers remain expanded and the adhesive infiltrates properly. However, if the collagen layer is dried, the fibers collapse, which prevents the adhesive from infiltrating fully. This also can negatively effect adhesion if gaps form between the adhesive and the dentin substrate. This collapse of the collagen fibers is a significant cause of post-operative sensitivity. 

A self-etch adhesive prevents this issue because the material etches and penetrates in one step, making the etching depth and the depth of the adhesive’s penetration the same. When bonding to dentin, the self-etch system prevents the collagen fibers from collapsing, and also eliminates the need for “moist” bonding.

Easy Bond adhesive therefore offers a tool that effectively delivers high bond strengths, but is less technique sensitive than a total-etch system. Additionally, it can be applied efficiently, and reduces the risk of post-operative sensitivity. In fact, a field evaluation of more than 5,000 restorations placed using the adhesive found less than 0.5% reported post-operative sensitivity. 

For extra insurance, practitioners may opt for the one-two punch of combining this adhesive with 3M ESPE Vitrebond Plus Light Cure Glass Ionomer Liner/Base.

This product creates a strong bond to dentin, sealing the tooth structure to protect against microleakage, which also helps reduce post-operative sensitivity. Additionally, the liner helps reduce the effect of composite shrinkage by more than 50 percent.

Practitioners who have practiced for many years may recall learning in dental school to use Copalite varnish and IRM as a base on deep cavity preps. Composite materials have led to a paradigm shift in restorative dentistry, but using a glass ionomer liner with a composite restoration can be likened to this earlier practice. The liner also gives practitioners the extra assurance of fluoride release.

The following case demonstrates the quick procedure used to apply these products in a posterior restoration.

The protocol

A 30-year-old man presented to the office with occlusal decay on the lower left second molar. We determined a composite restoration was the most appropriate treatment.

Step 1: A rubber dam and clamp were placed to isolate the tooth (Fig. 1).

Step 2: Decay was removed and sodium hypochlorite was swabbed on the tooth to disinfect the area (Fig. 2).

Step 3: Vitrebond Plus liner/base was dispensed onto a mixing pad and mixed for 10 seconds until it was smooth and glossy (Fig. 3). The material was then applied to the base of the cavity and light cured (Fig. 4).

Step 4:Adper Easy Bond adhesive was applied with an applicator (Fig. 5) and scrubbed on the surface of the cavity for 20 seconds (Fig. 6).

Step 5: The adhesive was air-thinned for 5 seconds, until the film no longer moved, indicating complete vaporization of the solvent (Fig. 7).

Step 6: The area was then light cured for 10 seconds (Fig. 8).

Step 7:3M ESPE Filtek™ Supreme Ultra Universal Restorative in shade A2 was applied and light cured (Fig. 9).

Step 8: The restoration was trimmed and shaped with diamond finishing burs and was completed with polishing points and cups (Fig. 10). Once finished, the restoration exhibited excellent esthetics, and the patient experienced no sensitivity following the procedure  (Fig. 11).

Discussion

The adhesive used in this case has a simple, fast and forgiving technique. Provided that practitioners thoroughly scrub the adhesive into the tooth surface for the full 20 seconds, they can be confident the material will perform properly, etching and penetrating in one step.

When combined with the glass ionomer liner, this technique produces long-lasting restorations with strong bonds that result in virtually no post-operative sensitivity. With these tools, practitioners can feel confident their patients will be comfortable and satisfied with their restorations.